1. Field of the Invention
This invention relates to a hand tool, and more particularly to a ratchet screwdriver that includes a replaceable bit magazine unit.
2. Description of the Related Art
Referring to FIGS. 1 and 2, a conventional screwdriver includes a screwdriver body 1, a sliding unit 2 disposed movably in the screwdriver body 1, a controlling member 3 operable to move the sliding unit 2 in the screwdriver body 1 along a straight path, a handle 4 disposed fixedly on the screwdriver body 1 and located behind the controlling member 3, and a bit magazine 5 journalled in the screwdriver body 1. The screwdriver body 1 includes a shaft seat 101 and a circular tube 102 connected fixedly to a rear end of the shaft seat 101. The shaft seat 101 has an annular outer surface that is formed with a recess 103. The circular tube 102 is formed with two open-ended axial slots 104. The sliding unit 2 includes a hook rod 201 and a guiding block 202. The hook rod 201 includes a hook portion 201′ disposed at a front end thereof, and an integral stub 203 disposed at a rear end thereof and extending through a hole 204 in the guiding block 202. A C-shaped retaining ring 205 is received within an annular groove 206 in the stub 203 so as to retain the guiding block 202 on the hook rod 201. The guiding block 202 is formed with two guiding rod portions 202′ at two opposite ends thereof, which extend respectively through the axial slots 104 in the circular tube 102. The bit magazine 5 is journalled within the recess 103 in the shaft seat 101 by a shaft 7, and has an annular outer surface that is formed with a plurality of bit slots 501 for receiving respectively a plurality of screwdriver bits 6 (only one is shown in FIG. 1) therein. Each of the bits 6 has an annular outer surface that is formed with an annular groove 601. The controlling member 3 can be rotated in a direction to move the sliding unit 2 rearwardly in the screwdriver body 1. When the sliding unit 2 moves to its rear limit position, the hook portion 201′ engages the annular groove 601 in a selected one of the bits 6. Subsequently, the controlling member 3 can be rotated in an opposite direction to move the sliding unit 2 forwardly. When the sliding unit 2 moves to its front limit position, the selected bit 6 projects from the screwdriver body 1 for performing a screw driving operation. The bit magazine 5 can be rotated manually within the screwdriver body 1 to change the bit 6 to be moved by the sliding unit 2.
The aforesaid conventional screwdriver suffers from the following disadvantages:
1. The bit magazine 5 cannot be removed from the screwdriver body 1 for replacement.
2. The bits 6 are put respectively into the bit slots 501 in the bit magazine 5 in a radial direction of the bit magazine 5. As such, the bits 6 are apt to become dislodged from the bit slots 501.
3. To allow for operation by the sliding unit 2, it is necessary for the bits 6 to be formed with the annular grooves 601. Current screwdriver bits are not suitable for use with said conventional screwdriver because they are not provided with annular grooves.
4. To perform a screw driving operation, the controlling member 3 must be rotated to move the sliding unit 2 in the screwdriver body 1. This results in a troublesome operation.
5. The conventional screwdriver is not provided with a ratchet unit.